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Electrochemical antioxidant screening and evaluation based on guanine and chitosan immobilized MoS2 nanosheet modified glassy carbon electrode (guanine/CS/MoS2/GCE)

  • Ping Tang EMAIL logo , Xiaosheng Tang , Shiyong Mei , Yixi Xie , Liangliang Liu EMAIL logo and Licheng Ren EMAIL logo
Published/Copyright: February 13, 2020
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Open Chemistry
From the journal Open Chemistry Volume 18 Issue 1

Abstract

In this study, an electrochemical biosensor based on guanine and chitosan immobilized MoS2 nanosheet modified glassy carbon electrode (guanine/CS/MoS2/GCE) was developed and employed for antioxidant screening and antioxidant capacity evaluation. The oxidation peak current of guanine was improved and nearly tripled after modifications of chitosan and MoS2 nanosheet. The immobilized guanine could be damaged by hydroxyl radicals generated in Fenton solution. However, in the presence of antioxidants, the guanine was protected and the oxidation peak current of guanine increased. This process mimics the mechanism of antioxidant protection in human body. The factors affecting preparation of sensor and detection of antioxidant capacity were optimized. At the optimum conditions, the guanine/CS/MoS2/GCE showed wide linear range, low detection limit, satisfactory reproducibility and stability for detection. Ascorbic acid was used as a model antioxidant to evaluate the antioxidant capacity. A good linearity was observed with a correlation coefficient of 0.9959 in the concentrations between 0.5 and 4.0 mg L-1. The antioxidant capacities of three flavonoids were also tested and the rank of antioxidant capacities was ascorbic acid (51.84%), quercetin (45.82%), fisetin (34.39%) and catechin (16.99%). Due to the rapid measurement and low cost, this sensor could provide an available sensing platform for antioxidant screening and evaluation.

Keywords: Antioxidant capacity; Chitosan; Guanine; Hydroxyl radical; MoS2 nanosheet

1 Introduction

There is a growing attention paid to the damage of living cells caused by oxidative stress, which is generally associated with the generation of reactive oxygen species (ROS). ROS includes oxygen radicals (O2·-, ·OH, RO2·, HO2·) and byproducts of nonradical oxidizing agents (H2O2, HOCl, O3) that can be easily converted into radicals [1]. When the level of ROS increases dramatically to cause oxidative stress, it could lead to cellular damage to DNA, proteins and lipids, as well as being linked with various human diseases such as rheumatoid arthritis, cardiovascular disorders, cancer and diabetes, etc. [2]. To protect living organisms and counteract the deleterious effects of ROS, complex and sophisticated endogenous and exogenous antioxidant systems are evolved in organisms [3]. The exogenous antioxidant system can be provided by chemical antioxidants such as ascorbic acid, phenolic compounds and flavonoids, which exist in fruit, vegetables and beverages. These antioxidants are important for the protection of human health [4]. Therefore, finding antioxidants and the following evaluation of antioxidant capacity for antioxidants has significant meaning in related research, and there is a high demand to explore rapid and appropriate methods for quantitative determination of antioxidants in real samples.

Several traditional analytical methods have been proposed for measuring the total antioxidant capacities in various samples. Usually, these analytical methods are based on photometric, chromatographic and fluorometric techniques [5, 6, 7]. However, the radicals used in these methods (DPPH·, ABTS+· or iron) are usually chemical reagents, which belong to exogenous ROS. And the corresponding measures of antioxidant capacities are chemical types as well. Moreover, unstable results and sophisticated procedures are other disadvantages with these methods. Therefore, the simulation of antioxidant mechanism and oxidative stress state taking place in vivo are helpful to explore effective and satisfactory antioxidants. However, this kind of simulation face more difficulties as well.

Recently, several ROS scavenging-type electrochemical antioxidant sensors have been developed and reported [8, 9, 10]. For this kind of biosensors, guanine is immobilized on electrodes as an oxidation target, and Fenton solutions are used for ·OH generation. However, the immobilization of guanine on electrodes suffers some drawbacks, such as inactivation, insufficient adsorption and complicated procedures. MoS2 nanosheet is one of the graphene-like two-dimensional layered materials [11]. It has advantages like large specific surface area, unique optical properties, high electrocatalytic ability, good biocompatibility, and so on [12, 13]. Due to the large specific surface area, MoS2 nanosheet shows a good adsorption performance and could improve the immobilization of guanine. Driven by this property, the immobilization of guanine on the surface of MoS2 nanosheet modified glassy carbon electrode (GCE) and subsequent activation of guanine are better than those of bare GCE. What’s more, good biocompatibility and nontoxicity of MoS2 nanosheet allow its development in biochemical and biological researches.

In this work, MoS2 nanosheet modified GCE (MoS2/GCE) is prepared, and then guanine and chitosan are immobilized on MoS2/GCE forming the guanine and chitosan immobilized MoS2 nanosheet modified glassy carbon electrode (guanine/CS/MoS2/GCE) as an electrochemical sensor for screening and evaluation of antioxidants. The working principle of this sensor is shown in Scheme 1. The ·OH radicals generated by Fenton solution could damage guanine and lead to the change of peak current in square wave voltammetry (SWV). In this process, MoS2 nanosheet serves as a co-catalyst and could greatly enhance the efficiency of ·OH radicals generation [14]. Large number of ·OH radicals generated on the surface of MoS2/GCE mimic the ROS environment and antioxidant protection mechanism in vivo. Meanwhile, ·OH radicals could be attracted by the glucoside bonds of chitosan. Hence, guanine could be damaged more completely under the existence of chitosan [15]. Compared with traditional methods, this sensor could directly determine the antioxidant capacity of target compound without extra processes. Therefore, this sensor could be applied in rapid detection of antioxidant capacity and screening of antioxidants from complexes.

2 Materials and Methods

2.1 Chemicals and reagents

Guanine, chitosan, MoS2 powder, ferrous sulfate and ethylenediaminetetraacetic acid (EDTA) were purchased from Merck KGaA (Darmstadt, Germany). Quercetin, fisetin and catechin were acquired from Shanghai Yuanye Biotechnology Co., Ltd (Shanghai, China). Voltammetric measurements were carried out in phosphate buffered solutions (PBS, 50 mM) as supporting electrolytes. Stock solutions of guanine (1 g L-1) were prepared by dissolving a certain amount of guanine in NaOH (0.1 M). Stock solutions of flavonoids (quercetin, fisetin and catechin) were prepared by dissolving the solid in ethanol. The working standard solutions were prepared daily by diluting stock solutions with supporting electrolytes to certain concentration. Fe2+-EDTA solution was prepared daily by adding definite amount of ferrous sulfate to EDTA solution (1 mM). Fenton solution for ·OH generation was carried out in a mixture of hydrogen peroxide (20 mM) and Fe2+-EDTA. Ultra-pure water (18.25 MΩ·cm, 25 °C) was obtained from a Millipore system (Millipore Corporation, Milford, MA, USA). All other chemicals were of analytical grade without further purification.

2.2 Apparatus

All electrochemical measurements were performed on a CHI 660E Electrochemical Workstation (Chenhua Instrument Company of Shanghai, Shanghai, China) with a standard three electrodes system including a glassy carbon electrode (GCE, a diameter of 3 mm) as the working electrode, a platinum wire as the auxiliary electrode and an Ag/AgCl (KCl 3.0 M) electrode as the reference electrode. All the potentials obtained in this study are reported against Ag/AgCl/KCl electrode. The morphology of MoS2 was obtained by using a scanning electron microscopy (SEM, JSM 6610Lv, JEOL, Japan) operated at 30 kV. An ultrasonic processor FS-250 (20% amplitude; Shanghai Shengxi, Shanghai, China) was used for synthesizing the MoS2 nanosheet. All the experiments were carried out at room temperature.

Scheme 1 The preparation process of the modified electrode and the detection method for guanine damage: SWV.
Scheme 1

The preparation process of the modified electrode and the detection method for guanine damage: SWV.

2.3 Preparation of MoS2 nanosheet

The MoS2 nanosheet was prepared by MoS2 powder according to literature [16] with some modifications. Briefly, 300 mg of MoS2 powders were dispersed in 100 mL of mixtures consisted of acetone and water (v:v, 89:11) to obtain MoS2 suspension (3 mg mL-1). Afterwards, the suspension was ultrasonically treated in iced water for 1 h using an ultrasonic processor FS-250 with pulsed ultrasonic irradiation mode (Power, 35 W; Pulse frequency: 20 s on and 10 s off) to attain MoS2 nanosheet. The pulsed ultrasonic irradiation mode could reduce solvent heating and avoid degradation of produced MoS2 nanosheet. Finally, the dispersion was centrifuged at 3000 rpm for 30 min (Beckman Coulter Allegra 64R, Brea, CA, USA). The supernatant was collected and dried in a vacuum oven for further use.

2.4 Preparation of the guanine/CS/MoS2/GCE

The MoS2 suspension (0.5 mg mL-1) was obtained by dispersing MoS2 nanosheet in water. The MoS2/GCE was obtained by dropping 6 μL of MoS2 suspension on the surface of a GCE and dried at room temperature to form a MoS2 film on the GCE. Then, chitosan solution (1.0 mg mL-1, in 1% acetic acid) was added to a guanine solution (0.6 mg mL-1) at a volume ratio of 1:5 (v/v), and then 6 μL of the mixture added on to the surface of MoS2/GCE and dried at room temperature. Ultimately, we obtained a guanine/CS/MoS2/GCE.

2.5 Antioxidant capacity assays

Hydroxyl (·OH) radicals could be produced by adding hydrogen peroxide into freshly prepared Fe2+-EDTA solution in PBS (50 mM, pH 3.5). Damage of guanine was performed by immersing the guanine/CS/MoS2/GCE in Fenton solution. After a certain incubation time, the guanine/CS/MoS2/GCE was washed with water and immersed in PBS (50 mM, pH 1.5) immediately to perform the SWV detection. The oxidation peak of guanine in SWV peaks was measured at about 1.20 V.

For antioxidant capacity assay, antioxidant (quercetin, fisetin and catechin) with a certain concentration was firstly added into freshly prepared Fenton solution. Then, the guanine/CS/MoS2/GCE was immersed in the Fenton solution containing antioxidant. After the same procedures as mentioned before, the SWV detection of guanine/CS/MoS2/GCE was performed as well. The oxidation peak of guanine in SWV peaks could be observed and used to calculate the antioxidant activity of sample. The antioxidant capacity of sample was calculated using the following equation:

(1)Antioxidant capacity %=(I0−Is)/(I0−Ic)×100

Where I0 is the oxidation peak current of guanine/CS/MoS2/GCE before damage in Fenton solution, Ic is the oxidation peak current after damage in Fenton solution without sample, and Is is the oxidation peak current after damage in Fenton solution with sample.

Ethical approval: The conducted research is not related to either human or animal use.

3 Results and discussion

3.1 Characterization of MoS2 nanosheet

The morphologies of MoS2 powder (Figure 1A) and MoS2 nanosheet (Figure 1B) were characterized by scanning electron microscopy (SEM). It could be observed in Figure 1A that the MoS2 powders were agglomerated by a large number of particles with 2 μm of diameter, and the particles were uniform in morphology. Figure 1B showed that the exfoliated MoS2 nanosheet with a typical layered and wrinkled structure. The SEM characterization confirmed that MoS2 nanosheet was successfully prepared from MoS2 powders.

Figure 1 SEM images of MoS2 powder (A) and MoS2 nanosheet (B).
Figure 1

SEM images of MoS2 powder (A) and MoS2 nanosheet (B).

3.2 Electrochemical study of the guanine/CS/MoS2/GCE

Figure 2 showed the SWV results of guanine/GCE (a), guanine/CS/GCE (b) and guanine/CS/MoS2/GCE (c) in PBS (50 mM, pH 1.5). It can be noted from the picture that an oxidation peak potential of guanine appeared at about 1.20 V. When the guanine molecules were previously mixed with chitosan and then immobilized together on the electrode, the corresponding oxidation peak current got a clear improvement (Figure 2b). It indicated that chitosan could effectively adsorb guanine to the surface of electrode. Moreover, the oxidation peak current of guanine on the guanine/CS/MoS2/GCE is 42.6 μA, which is nearly 3 times than that on the guanine/GCE (15.2 μA). This might be due to the good adsorption performance and biocompatibility of MoS2 nanosheet.

Figure 2 SWVs obtained at the guanine/GCE (a), guanine/CS/GCE (b) and guanine/CS/MoS2/GCE (c) in PBS (50 mM, pH 1.5).
Figure 2

SWVs obtained at the guanine/GCE (a), guanine/CS/GCE (b) and guanine/CS/MoS2/GCE (c) in PBS (50 mM, pH 1.5).

In order to get a better understanding about the interaction between chitosan and guanine, the geometry of chitosan and guanine was optimized with the density functional theory method (B3LYP/6-31G*). The density functional theory [17] B3LYP/6-31G* basis set was employed to optimize the guanine and chitosan without any constraints via the Gaussian software [18]. The B3LYP functional includes Becke’s three-parameter-exchange functional and Lee-Young-Parr correlation functional [19, 20, 21]. Figure 3 showed the optimized structures and the electrostatic potential surface of aromatic systems of guanine (a) and chitosan (b). Electrostatic potentials were caused by the interactions of electrons or nuclei with electrons [22, 23]. The blue area corresponded to the negative charges. The red region expressed the positive charges. As shown in Figure 3, the N6 and N11 atom in guanine had negative charges. However, the positive charges have been found in the amino unit of chitosan which was consisted well with previous experiment [24]. It indicated that chitosan and guanine could bind together well with electrostatic interaction.

Figure 3 The optimized structure of guanine (a) and chitosan (b) and electrostatic potential surface of aromatic systems calculated at B3LYP/ 6-31G*.
Figure 3

The optimized structure of guanine (a) and chitosan (b) and electrostatic potential surface of aromatic systems calculated at B3LYP/ 6-31G*.

3.3 Effect of pH and immobilized concentration

The effect of pH value on the electrochemical response of guanine on guanine/CS/MoS2/GCE was studied by SWV and the results were shown in Figure 4A. An insert displayed a plot of guanine electro-oxidation signals with the change of pH. The oxidation peak currents decreased gradually with the increasing of pH values. The response reached the maximum value at pH 1.5. The oxidation peak potentials obeyed the equation in the range of pH from 1.5 to 4.0 (Figure 4B), Ep = 1.288 – 0.0696 pH (R2 = 0.9861). The calculated slope (69.6 mV pH-1) was closed to the theoretical value of 59 mV indicating that direct electrooxidation of guanine is an isoelectron and isoproton process [25, 26]. Therefore, 50 mM phosphate buffered solution with pH 1.5 was used as the supporting electrolyte in all electrochemical determinations during this research.

Figure 4 (A) Effect of pH on the electrochemical response of guanine on the guanine/CS/MoS2/GCE. Insert: relationship between oxidant peak current and pH. (B) The calibration plot of potential against pH. The experimental conditions were incubated in Fenton solution (1 mM EDTA, 2.0 mM Fe2+ ions and 20 mM H2O2) for 300 s.
Figure 4

(A) Effect of pH on the electrochemical response of guanine on the guanine/CS/MoS2/GCE. Insert: relationship between oxidant peak current and pH. (B) The calibration plot of potential against pH. The experimental conditions were incubated in Fenton solution (1 mM EDTA, 2.0 mM Fe2+ ions and 20 mM H2O2) for 300 s.

The amount of modifiers on the surface of electrode is one of the important factors that influence the voltammetric response of guanine. As shown in Figure 5, the peak currents increased gradually with the increase of guanine/CS concentrations (from 0.1 to 0.6 mg mL-1) and decreased rapidly when the concentration was higher than 0.6 mg mL-1. This result might indicate that the thicker film of guanine/CS blocked the electron transfer between guanine and electrode. Therefore, 0.6 mg mL-1 of guanine/CS suspension was chosen as the optimum concentration to modify the GCE.

Figure 5 Effect of immobilized concentration on the electrochemical response of guanine on the guanine/CS/MoS2/GCE. The experimental conditions were incubated in Fenton solution (1 mM EDTA, 2.0 mM Fe2+ ions and 20 mM H2O2) for 300 s.
Figure 5

Effect of immobilized concentration on the electrochemical response of guanine on the guanine/CS/MoS2/GCE. The experimental conditions were incubated in Fenton solution (1 mM EDTA, 2.0 mM Fe2+ ions and 20 mM H2O2) for 300 s.

3.4 Optimization of electrochemical assays

Hydroxyl radicals (·OH) are part of reactive oxygen species in living systems, which are generated from the metal ion-dependent breakdown of hydrogen peroxide. The ·OH produced by Fenton’s reaction plays a major role during oxidative damage in vivo. EDTA is usually used as a chelating agent in Fenton solution to increase the solubility of Fe2+ ions. Meanwhile, MoS2 nanosheet could enhance the efficiency of ·OH generation as a co-catalyst. Therefore, Fenton solution containing EDTA was used to generate ·OH for the damage of guanine on electrode in this study.

Reported studies indicated that the concentration of Fe2+ ions had a close relationship with the production of ·OH and affected the damage of guanine [27]. The relationship between concentration of Fe2+ ions and electrochemical oxidation peak current of guanine/CS/MoS2/GCE was studied. As shown in Figure 6, it could be observed that the peak currents decreased with increasement of Fe2+ ions. When the concentration of Fe2+ ions is higher than about 2.0 mM, the change of peak current tended to gentle.

Figure 6 (A) The oxidation peak current of the guanine/CS/MoS2/GCE after incubation for 300 s in Fenton solution (1 mM EDTA and 20 mM H2O2) with different concentration of Fe2+ ions (a-i): 0, 0.3, 0.5, 0.8, 1.0, 1.5, 2.0, 2.5 and 3.0 mM. (B) The relationship between oxidant peak current and the concentration of Fe2+ ions.
Figure 6

(A) The oxidation peak current of the guanine/CS/MoS2/GCE after incubation for 300 s in Fenton solution (1 mM EDTA and 20 mM H2O2) with different concentration of Fe2+ ions (a-i): 0, 0.3, 0.5, 0.8, 1.0, 1.5, 2.0, 2.5 and 3.0 mM. (B) The relationship between oxidant peak current and the concentration of Fe2+ ions.

Incubation time could affect the damage degree of guanine. Therefore, the effect of incubation time was also investigated in this study (Figure 7). With the incubation time increased, the peak currents decreased gradually until the incubation time reached 300 s. It indicated that 300 s incubation was enough for guanine damage. Therefore, 2.0 mM Fe2+ ions and 300 s incubation time were chosen as experimental conditions for future studies.

Figure 7 Effect of incubation time of the guanine/CS/MoS2/GCE with the Fenton solution (1 mM EDTA, 2.0 mM Fe2+ ions and 20 mM H2O2).
Figure 7

Effect of incubation time of the guanine/CS/MoS2/GCE with the Fenton solution (1 mM EDTA, 2.0 mM Fe2+ ions and 20 mM H2O2).

3.5 Antioxidant capacity assays

The ·OH generated by Fenton solution could attack electrode surface and damage guanine molecules. When antioxidants were added into Fenton solution, the produced ·OH was scavenged by antioxidants and correspondingly the damage of guanine was reduced. Through the electrochemical detection, a higher oxidation peak current of guanine could be observed and the antioxidant capacity could be then calculated.

As a well-known and powerful antioxidant, ascorbic acid (AA) is regarded as an important water-soluble ROS scavenger in human body [28]. In this work, AA was selected as a model antioxidant to evaluate the antioxidant capacity performance in developed electrochemical biosensor. Figure 8A showed the SWV curves of guanine/CS/MoS2/GCE incubated for 300 s in Fenton solution (1 mM EDTA, 2.0 mM Fe2+ ions and 20 mM H2O2) with different concentrations of AA. Figure 8B showed the plots of peak currents against AA concentrations. It was noted that the presence of AA significantly affected the oxidation peak current, and the peak current increased with increasing concentration of AA. A linear relationship of peak current and AA concentration was also observed (Figure 8B) when the concentration of AA was between 0.5 and 4.0 mg L-1. The corresponding linear function was Ip (μA) = -4.4395 CAA – 18.2693 with a correlation coefficient of R2 = 0.9959. The detection limit was calculated to be 0.33 mg L-1 (S/N = 3). Based on these results, it could be considered the developed sensor showed good linear range and detection limit.

Figure 8 (A) The oxidation peak current of the guanine/CS/MoS2/GCE after incubation for 300 s in Fenton solution (1 mM EDTA, 2.0 mM Fe2+ ions and 20 mM H2O2) with different concentration of AA (a-i): 0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5 and 4.0 mg L-1. (B) The calibration plot of oxidant peak current against the concentration of AA.
Figure 8

(A) The oxidation peak current of the guanine/CS/MoS2/GCE after incubation for 300 s in Fenton solution (1 mM EDTA, 2.0 mM Fe2+ ions and 20 mM H2O2) with different concentration of AA (a-i): 0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5 and 4.0 mg L-1. (B) The calibration plot of oxidant peak current against the concentration of AA.

In order to confirm the abilities in antioxidant capacity detection and antioxidant screening of proposed sensor, the antioxidant capacities of several flavonoids were analyzed by guanine/CS/MoS2/GCE. The concentration of antioxidant in this assay was set at 2.0 mg L-1. Figure 9 presented the results of antioxidant capacities for three flavonoids and AA. AA displayed the highest antioxidant capacity (51.84%), then followed by quercetin (45.82%), fisetin (34.39%) and catechin (16.99%). Three investigated flavonoids showed different antioxidant capacities, which showed this sensor could be used for evaluation of samples.

Figure 9 Antioxidant screening of several antioxidant compounds using the guanine/CS/MoS2/GCE electrode.
Figure 9

Antioxidant screening of several antioxidant compounds using the guanine/CS/MoS2/GCE electrode.

3.6 Reproducibility and stability tests

The reproducibility and stability of modified electrode were also evaluated by detecting AA (2.0 mg L-1) in Fenton solution. As shown in Figure 10, Different electrodes were used for 10 times of parallel measurements (Black plots), and it showed a good reproducibility with the relative standard deviation is 2.9%. The same electrode was also tested for 10 times of parallel measurements (Red plots), and it showed a better reproducibility with the relative standard deviation of 1.2%. The modified electrode was stored at the room temperature (25°C) for a week. The current of electrode was reduced about 1.8%. The modified electrode displayed acceptable reproducibility and stability, indicating that the guanine/CS/MoS2/GCE is suitable for antioxidant screening.

Figure 10 The reproducibility of guanine/CS/MoS2/GCE (Black: different electrodes; Red: the same electrode) in detection of AA (2.0 mg L-1). The experimental conditions were incubated in Fenton solution (1 mM EDTA, 2.0 mM Fe2+ ions and 20 mM H2O2) for 300 s.
Figure 10

The reproducibility of guanine/CS/MoS2/GCE (Black: different electrodes; Red: the same electrode) in detection of AA (2.0 mg L-1). The experimental conditions were incubated in Fenton solution (1 mM EDTA, 2.0 mM Fe2+ ions and 20 mM H2O2) for 300 s.

4 Conclusions

In this study, the guanine/CS/MoS2/GCE was assembled and investigated as an electrochemical biosensor for antioxidant screening and antioxidant capacity test. Due to the co-catalyst and adsorption effects of MoS2 nanosheet, the detection could mimic the antioxidant protection mechanism in vivo. The factors affected preparation of sensor and detection of antioxidant capacity were optimized. Under the optimum conditions, the guanine/CS/MoS2/GCE showed advantages like wide linear range, low detection limit, satisfactory reproducibility and stability. The antioxidant capacities of three flavonoids were also tested and compared with AA. As a result, the rank of antioxidant capacity was AA (51.84%), quercetin (45.82%), fisetin (34.39%) and catechin (16.99%). The proposed biosensor provided a rapid and inexpensive sensing platform for antioxidant screening and evaluation.

Acknowledgments

This work was supported by Science and Technology Research Project of Hubei Province Education Department (B2018245).

  1. Conflicts of Interest: The authors declare no conflict of interest.

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Received: 2019-08-05
Accepted: 2019-12-11
Published Online: 2020-02-13

© 2020 B. Ping Tang et al., published by De Gruyter

This work is licensed under the Creative Commons Attribution 4.0 International License.

Articles in the same Issue

  1. Regular Articles
  2. Electrochemical antioxidant screening and evaluation based on guanine and chitosan immobilized MoS2 nanosheet modified glassy carbon electrode (guanine/CS/MoS2/GCE)
  3. Kinetic models of the extraction of vanillic acid from pumpkin seeds
  4. On the maximum ABC index of bipartite graphs without pendent vertices
  5. Estimation of the total antioxidant potential in the meat samples using thin-layer chromatography
  6. Molecular dynamics simulation of sI methane hydrate under compression and tension
  7. Spatial distribution and potential ecological risk assessment of some trace elements in sediments and grey mangrove (Avicennia marina) along the Arabian Gulf coast, Saudi Arabia
  8. Amino-functionalized graphene oxide for Cr(VI), Cu(II), Pb(II) and Cd(II) removal from industrial wastewater
  9. Chemical composition and in vitro activity of Origanum vulgare L., Satureja hortensis L., Thymus serpyllum L. and Thymus vulgaris L. essential oils towards oral isolates of Candida albicans and Candida glabrata
  10. Effect of excess Fluoride consumption on Urine-Serum Fluorides, Dental state and Thyroid Hormones among children in “Talab Sarai” Punjab Pakistan
  11. Design, Synthesis and Characterization of Novel Isoxazole Tagged Indole Hybrid Compounds
  12. Comparison of kinetic and enzymatic properties of intracellular phosphoserine aminotransferases from alkaliphilic and neutralophilic bacteria
  13. Green Organic Solvent-Free Oxidation of Alkylarenes with tert-Butyl Hydroperoxide Catalyzed by Water-Soluble Copper Complex
  14. Ducrosia ismaelis Asch. essential oil: chemical composition profile and anticancer, antimicrobial and antioxidant potential assessment
  15. DFT calculations as an efficient tool for prediction of Raman and infra-red spectra and activities of newly synthesized cathinones
  16. Influence of Chemical Osmosis on Solute Transport and Fluid Velocity in Clay Soils
  17. A New fatty acid and some triterpenoids from propolis of Nkambe (North-West Region, Cameroon) and evaluation of the antiradical scavenging activity of their extracts
  18. Antiplasmodial Activity of Stigmastane Steroids from Dryobalanops oblongifolia Stem Bark
  19. Rapid identification of direct-acting pancreatic protectants from Cyclocarya paliurus leaves tea by the method of serum pharmacochemistry combined with target cell extraction
  20. Immobilization of Pseudomonas aeruginosa static biomass on eggshell powder for on-line preconcentration and determination of Cr (VI)
  21. Assessment of methyl 2-({[(4,6-dimethoxypyrimidin-2-yl)carbamoyl] sulfamoyl}methyl)benzoate through biotic and abiotic degradation modes
  22. Stability of natural polyphenol fisetin in eye drops Stability of fisetin in eye drops
  23. Production of a bioflocculant by using activated sludge and its application in Pb(II) removal from aqueous solution
  24. Molecular Properties of Carbon Crystal Cubic Structures
  25. Synthesis and characterization of calcium carbonate whisker from yellow phosphorus slag
  26. Study on the interaction between catechin and cholesterol by the density functional theory
  27. Analysis of some pharmaceuticals in the presence of their synthetic impurities by applying hybrid micelle liquid chromatography
  28. Two mixed-ligand coordination polymers based on 2,5-thiophenedicarboxylic acid and flexible N-donor ligands: the protective effect on periodontitis via reducing the release of IL-1β and TNF-α
  29. Incorporation of silver stearate nanoparticles in methacrylate polymeric monoliths for hemeprotein isolation
  30. Development of ultrasound-assisted dispersive solid-phase microextraction based on mesoporous carbon coated with silica@iron oxide nanocomposite for preconcentration of Te and Tl in natural water systems
  31. N,N′-Bis[2-hydroxynaphthylidene]/[2-methoxybenzylidene]amino]oxamides and their divalent manganese complexes: Isolation, spectral characterization, morphology, antibacterial and cytotoxicity against leukemia cells
  32. Determination of the content of selected trace elements in Polish commercial fruit juices and health risk assessment
  33. Diorganotin(iv) benzyldithiocarbamate complexes: synthesis, characterization, and thermal and cytotoxicity study
  34. Keratin 17 is induced in prurigo nodularis lesions
  35. Anticancer, antioxidant, and acute toxicity studies of a Saudi polyherbal formulation, PHF5
  36. LaCoO3 perovskite-type catalysts in syngas conversion
  37. Comparative studies of two vegetal extracts from Stokesia laevis and Geranium pratense: polyphenol profile, cytotoxic effect and antiproliferative activity
  38. Fragmentation pattern of certain isatin–indole antiproliferative conjugates with application to identify their in vitro metabolic profiles in rat liver microsomes by liquid chromatography tandem mass spectrometry
  39. Investigation of polyphenol profile, antioxidant activity and hepatoprotective potential of Aconogonon alpinum (All.) Schur roots
  40. Lead discovery of a guanidinyl tryptophan derivative on amyloid cascade inhibition
  41. Physicochemical evaluation of the fruit pulp of Opuntia spp growing in the Mediterranean area under hard climate conditions
  42. Electronic structural properties of amino/hydroxyl functionalized imidazolium-based bromide ionic liquids
  43. New Schiff bases of 2-(quinolin-8-yloxy)acetohydrazide and their Cu(ii), and Zn(ii) metal complexes: their in vitro antimicrobial potentials and in silico physicochemical and pharmacokinetics properties
  44. Treatment of adhesions after Achilles tendon injury using focused ultrasound with targeted bFGF plasmid-loaded cationic microbubbles
  45. Synthesis of orotic acid derivatives and their effects on stem cell proliferation
  46. Chirality of β2-agonists. An overview of pharmacological activity, stereoselective analysis, and synthesis
  47. Fe3O4@urea/HITh-SO3H as an efficient and reusable catalyst for the solvent-free synthesis of 7-aryl-8H-benzo[h]indeno[1,2-b]quinoline-8-one and indeno[2′,1′:5,6]pyrido[2,3-d]pyrimidine derivatives
  48. Adsorption kinetic characteristics of molybdenum in yellow-brown soil in response to pH and phosphate
  49. Enhancement of thermal properties of bio-based microcapsules intended for textile applications
  50. Exploring the effect of khat (Catha edulis) chewing on the pharmacokinetics of the antiplatelet drug clopidogrel in rats using the newly developed LC-MS/MS technique
  51. A green strategy for obtaining anthraquinones from Rheum tanguticum by subcritical water
  52. Cadmium (Cd) chloride affects the nutrient uptake and Cd-resistant bacterium reduces the adsorption of Cd in muskmelon plants
  53. Removal of H2S by vermicompost biofilter and analysis on bacterial community
  54. Structural cytotoxicity relationship of 2-phenoxy(thiomethyl)pyridotriazolopyrimidines: Quantum chemical calculations and statistical analysis
  55. A self-breaking supramolecular plugging system as lost circulation material in oilfield
  56. Synthesis, characterization, and pharmacological evaluation of thiourea derivatives
  57. Application of drug–metal ion interaction principle in conductometric determination of imatinib, sorafenib, gefitinib and bosutinib
  58. Synthesis and characterization of a novel chitosan-grafted-polyorthoethylaniline biocomposite and utilization for dye removal from water
  59. Optimisation of urine sample preparation for shotgun proteomics
  60. DFT investigations on arylsulphonyl pyrazole derivatives as potential ligands of selected kinases
  61. Treatment of Parkinson’s disease using focused ultrasound with GDNF retrovirus-loaded microbubbles to open the blood–brain barrier
  62. New derivatives of a natural nordentatin
  63. Fluorescence biomarkers of malignant melanoma detectable in urine
  64. Study of the remediation effects of passivation materials on Pb-contaminated soil
  65. Saliva proteomic analysis reveals possible biomarkers of renal cell carcinoma
  66. Withania frutescens: Chemical characterization, analgesic, anti-inflammatory, and healing activities
  67. Design, synthesis and pharmacological profile of (−)-verbenone hydrazones
  68. Synthesis of magnesium carbonate hydrate from natural talc
  69. Stability-indicating HPLC-DAD assay for simultaneous quantification of hydrocortisone 21 acetate, dexamethasone, and fluocinolone acetonide in cosmetics
  70. A novel lactose biosensor based on electrochemically synthesized 3,4-ethylenedioxythiophene/thiophene (EDOT/Th) copolymer
  71. Citrullus colocynthis (L.) Schrad: Chemical characterization, scavenging and cytotoxic activities
  72. Development and validation of a high performance liquid chromatography/diode array detection method for estrogen determination: Application to residual analysis in meat products
  73. PCSK9 concentrations in different stages of subclinical atherosclerosis and their relationship with inflammation
  74. Development of trace analysis for alkyl methanesulfonates in the delgocitinib drug substance using GC-FID and liquid–liquid extraction with ionic liquid
  75. Electrochemical evaluation of the antioxidant capacity of natural compounds on glassy carbon electrode modified with guanine-, polythionine-, and nitrogen-doped graphene
  76. A Dy(iii)–organic framework as a fluorescent probe for highly selective detection of picric acid and treatment activity on human lung cancer cells
  77. A Zn(ii)–organic cage with semirigid ligand for solvent-free cyanosilylation and inhibitory effect on ovarian cancer cell migration and invasion ability via regulating mi-RNA16 expression
  78. Polyphenol content and antioxidant activities of Prunus padus L. and Prunus serotina L. leaves: Electrochemical and spectrophotometric approach and their antimicrobial properties
  79. The combined use of GC, PDSC and FT-IR techniques to characterize fat extracted from commercial complete dry pet food for adult cats
  80. MALDI-TOF MS profiling in the discovery and identification of salivary proteomic patterns of temporomandibular joint disorders
  81. Concentrations of dioxins, furans and dioxin-like PCBs in natural animal feed additives
  82. Structure and some physicochemical and functional properties of water treated under ammonia with low-temperature low-pressure glow plasma of low frequency
  83. Mesoscale nanoparticles encapsulated with emodin for targeting antifibrosis in animal models
  84. Amine-functionalized magnetic activated carbon as an adsorbent for preconcentration and determination of acidic drugs in environmental water samples using HPLC-DAD
  85. Antioxidant activity as a response to cadmium pollution in three durum wheat genotypes differing in salt-tolerance
  86. A promising naphthoquinone [8-hydroxy-2-(2-thienylcarbonyl)naphtho[2,3-b]thiophene-4,9-dione] exerts anti-colorectal cancer activity through ferroptosis and inhibition of MAPK signaling pathway based on RNA sequencing
  87. Synthesis and efficacy of herbicidal ionic liquids with chlorsulfuron as the anion
  88. Effect of isovalent substitution on the crystal structure and properties of two-slab indates BaLa2−xSmxIn2O7
  89. Synthesis, spectral and thermo-kinetics explorations of Schiff-base derived metal complexes
  90. An improved reduction method for phase stability testing in the single-phase region
  91. Comparative analysis of chemical composition of some commercially important fishes with an emphasis on various Malaysian diets
  92. Development of a solventless stir bar sorptive extraction/thermal desorption large volume injection capillary gas chromatographic-mass spectrometric method for ultra-trace determination of pyrethroids pesticides in river and tap water samples
  93. A turbidity sensor development based on NL-PI observers: Experimental application to the control of a Sinaloa’s River Spirulina maxima cultivation
  94. Deep desulfurization of sintering flue gas in iron and steel works based on low-temperature oxidation
  95. Investigations of metallic elements and phenolics in Chinese medicinal plants
  96. Influence of site-classification approach on geochemical background values
  97. Effects of ageing on the surface characteristics and Cu(ii) adsorption behaviour of rice husk biochar in soil
  98. Adsorption and sugarcane-bagasse-derived activated carbon-based mitigation of 1-[2-(2-chloroethoxy)phenyl]sulfonyl-3-(4-methoxy-6-methyl-1,3,5-triazin-2-yl) urea-contaminated soils
  99. Antimicrobial and antifungal activities of bifunctional cooper(ii) complexes with non-steroidal anti-inflammatory drugs, flufenamic, mefenamic and tolfenamic acids and 1,10-phenanthroline
  100. Application of selenium and silicon to alleviate short-term drought stress in French marigold (Tagetes patula L.) as a model plant species
  101. Screening and analysis of xanthine oxidase inhibitors in jute leaves and their protective effects against hydrogen peroxide-induced oxidative stress in cells
  102. Synthesis and physicochemical studies of a series of mixed-ligand transition metal complexes and their molecular docking investigations against Coronavirus main protease
  103. A study of in vitro metabolism and cytotoxicity of mephedrone and methoxetamine in human and pig liver models using GC/MS and LC/MS analyses
  104. A new phenyl alkyl ester and a new combretin triterpene derivative from Combretum fragrans F. Hoffm (Combretaceae) and antiproliferative activity
  105. Erratum
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https://doi.org/10.1515/chem-2020-0003
Keywords for this article
Antioxidant capacity; Chitosan; Guanine; Hydroxyl radical; MoS2 nanosheet
Creative Commons
BY 4.0

Articles in the same Issue

  1. Regular Articles
  2. Electrochemical antioxidant screening and evaluation based on guanine and chitosan immobilized MoS2 nanosheet modified glassy carbon electrode (guanine/CS/MoS2/GCE)
  3. Kinetic models of the extraction of vanillic acid from pumpkin seeds
  4. On the maximum ABC index of bipartite graphs without pendent vertices
  5. Estimation of the total antioxidant potential in the meat samples using thin-layer chromatography
  6. Molecular dynamics simulation of sI methane hydrate under compression and tension
  7. Spatial distribution and potential ecological risk assessment of some trace elements in sediments and grey mangrove (Avicennia marina) along the Arabian Gulf coast, Saudi Arabia
  8. Amino-functionalized graphene oxide for Cr(VI), Cu(II), Pb(II) and Cd(II) removal from industrial wastewater
  9. Chemical composition and in vitro activity of Origanum vulgare L., Satureja hortensis L., Thymus serpyllum L. and Thymus vulgaris L. essential oils towards oral isolates of Candida albicans and Candida glabrata
  10. Effect of excess Fluoride consumption on Urine-Serum Fluorides, Dental state and Thyroid Hormones among children in “Talab Sarai” Punjab Pakistan
  11. Design, Synthesis and Characterization of Novel Isoxazole Tagged Indole Hybrid Compounds
  12. Comparison of kinetic and enzymatic properties of intracellular phosphoserine aminotransferases from alkaliphilic and neutralophilic bacteria
  13. Green Organic Solvent-Free Oxidation of Alkylarenes with tert-Butyl Hydroperoxide Catalyzed by Water-Soluble Copper Complex
  14. Ducrosia ismaelis Asch. essential oil: chemical composition profile and anticancer, antimicrobial and antioxidant potential assessment
  15. DFT calculations as an efficient tool for prediction of Raman and infra-red spectra and activities of newly synthesized cathinones
  16. Influence of Chemical Osmosis on Solute Transport and Fluid Velocity in Clay Soils
  17. A New fatty acid and some triterpenoids from propolis of Nkambe (North-West Region, Cameroon) and evaluation of the antiradical scavenging activity of their extracts
  18. Antiplasmodial Activity of Stigmastane Steroids from Dryobalanops oblongifolia Stem Bark
  19. Rapid identification of direct-acting pancreatic protectants from Cyclocarya paliurus leaves tea by the method of serum pharmacochemistry combined with target cell extraction
  20. Immobilization of Pseudomonas aeruginosa static biomass on eggshell powder for on-line preconcentration and determination of Cr (VI)
  21. Assessment of methyl 2-({[(4,6-dimethoxypyrimidin-2-yl)carbamoyl] sulfamoyl}methyl)benzoate through biotic and abiotic degradation modes
  22. Stability of natural polyphenol fisetin in eye drops Stability of fisetin in eye drops
  23. Production of a bioflocculant by using activated sludge and its application in Pb(II) removal from aqueous solution
  24. Molecular Properties of Carbon Crystal Cubic Structures
  25. Synthesis and characterization of calcium carbonate whisker from yellow phosphorus slag
  26. Study on the interaction between catechin and cholesterol by the density functional theory
  27. Analysis of some pharmaceuticals in the presence of their synthetic impurities by applying hybrid micelle liquid chromatography
  28. Two mixed-ligand coordination polymers based on 2,5-thiophenedicarboxylic acid and flexible N-donor ligands: the protective effect on periodontitis via reducing the release of IL-1β and TNF-α
  29. Incorporation of silver stearate nanoparticles in methacrylate polymeric monoliths for hemeprotein isolation
  30. Development of ultrasound-assisted dispersive solid-phase microextraction based on mesoporous carbon coated with silica@iron oxide nanocomposite for preconcentration of Te and Tl in natural water systems
  31. N,N′-Bis[2-hydroxynaphthylidene]/[2-methoxybenzylidene]amino]oxamides and their divalent manganese complexes: Isolation, spectral characterization, morphology, antibacterial and cytotoxicity against leukemia cells
  32. Determination of the content of selected trace elements in Polish commercial fruit juices and health risk assessment
  33. Diorganotin(iv) benzyldithiocarbamate complexes: synthesis, characterization, and thermal and cytotoxicity study
  34. Keratin 17 is induced in prurigo nodularis lesions
  35. Anticancer, antioxidant, and acute toxicity studies of a Saudi polyherbal formulation, PHF5
  36. LaCoO3 perovskite-type catalysts in syngas conversion
  37. Comparative studies of two vegetal extracts from Stokesia laevis and Geranium pratense: polyphenol profile, cytotoxic effect and antiproliferative activity
  38. Fragmentation pattern of certain isatin–indole antiproliferative conjugates with application to identify their in vitro metabolic profiles in rat liver microsomes by liquid chromatography tandem mass spectrometry
  39. Investigation of polyphenol profile, antioxidant activity and hepatoprotective potential of Aconogonon alpinum (All.) Schur roots
  40. Lead discovery of a guanidinyl tryptophan derivative on amyloid cascade inhibition
  41. Physicochemical evaluation of the fruit pulp of Opuntia spp growing in the Mediterranean area under hard climate conditions
  42. Electronic structural properties of amino/hydroxyl functionalized imidazolium-based bromide ionic liquids
  43. New Schiff bases of 2-(quinolin-8-yloxy)acetohydrazide and their Cu(ii), and Zn(ii) metal complexes: their in vitro antimicrobial potentials and in silico physicochemical and pharmacokinetics properties
  44. Treatment of adhesions after Achilles tendon injury using focused ultrasound with targeted bFGF plasmid-loaded cationic microbubbles
  45. Synthesis of orotic acid derivatives and their effects on stem cell proliferation
  46. Chirality of β2-agonists. An overview of pharmacological activity, stereoselective analysis, and synthesis
  47. Fe3O4@urea/HITh-SO3H as an efficient and reusable catalyst for the solvent-free synthesis of 7-aryl-8H-benzo[h]indeno[1,2-b]quinoline-8-one and indeno[2′,1′:5,6]pyrido[2,3-d]pyrimidine derivatives
  48. Adsorption kinetic characteristics of molybdenum in yellow-brown soil in response to pH and phosphate
  49. Enhancement of thermal properties of bio-based microcapsules intended for textile applications
  50. Exploring the effect of khat (Catha edulis) chewing on the pharmacokinetics of the antiplatelet drug clopidogrel in rats using the newly developed LC-MS/MS technique
  51. A green strategy for obtaining anthraquinones from Rheum tanguticum by subcritical water
  52. Cadmium (Cd) chloride affects the nutrient uptake and Cd-resistant bacterium reduces the adsorption of Cd in muskmelon plants
  53. Removal of H2S by vermicompost biofilter and analysis on bacterial community
  54. Structural cytotoxicity relationship of 2-phenoxy(thiomethyl)pyridotriazolopyrimidines: Quantum chemical calculations and statistical analysis
  55. A self-breaking supramolecular plugging system as lost circulation material in oilfield
  56. Synthesis, characterization, and pharmacological evaluation of thiourea derivatives
  57. Application of drug–metal ion interaction principle in conductometric determination of imatinib, sorafenib, gefitinib and bosutinib
  58. Synthesis and characterization of a novel chitosan-grafted-polyorthoethylaniline biocomposite and utilization for dye removal from water
  59. Optimisation of urine sample preparation for shotgun proteomics
  60. DFT investigations on arylsulphonyl pyrazole derivatives as potential ligands of selected kinases
  61. Treatment of Parkinson’s disease using focused ultrasound with GDNF retrovirus-loaded microbubbles to open the blood–brain barrier
  62. New derivatives of a natural nordentatin
  63. Fluorescence biomarkers of malignant melanoma detectable in urine
  64. Study of the remediation effects of passivation materials on Pb-contaminated soil
  65. Saliva proteomic analysis reveals possible biomarkers of renal cell carcinoma
  66. Withania frutescens: Chemical characterization, analgesic, anti-inflammatory, and healing activities
  67. Design, synthesis and pharmacological profile of (−)-verbenone hydrazones
  68. Synthesis of magnesium carbonate hydrate from natural talc
  69. Stability-indicating HPLC-DAD assay for simultaneous quantification of hydrocortisone 21 acetate, dexamethasone, and fluocinolone acetonide in cosmetics
  70. A novel lactose biosensor based on electrochemically synthesized 3,4-ethylenedioxythiophene/thiophene (EDOT/Th) copolymer
  71. Citrullus colocynthis (L.) Schrad: Chemical characterization, scavenging and cytotoxic activities
  72. Development and validation of a high performance liquid chromatography/diode array detection method for estrogen determination: Application to residual analysis in meat products
  73. PCSK9 concentrations in different stages of subclinical atherosclerosis and their relationship with inflammation
  74. Development of trace analysis for alkyl methanesulfonates in the delgocitinib drug substance using GC-FID and liquid–liquid extraction with ionic liquid
  75. Electrochemical evaluation of the antioxidant capacity of natural compounds on glassy carbon electrode modified with guanine-, polythionine-, and nitrogen-doped graphene
  76. A Dy(iii)–organic framework as a fluorescent probe for highly selective detection of picric acid and treatment activity on human lung cancer cells
  77. A Zn(ii)–organic cage with semirigid ligand for solvent-free cyanosilylation and inhibitory effect on ovarian cancer cell migration and invasion ability via regulating mi-RNA16 expression
  78. Polyphenol content and antioxidant activities of Prunus padus L. and Prunus serotina L. leaves: Electrochemical and spectrophotometric approach and their antimicrobial properties
  79. The combined use of GC, PDSC and FT-IR techniques to characterize fat extracted from commercial complete dry pet food for adult cats
  80. MALDI-TOF MS profiling in the discovery and identification of salivary proteomic patterns of temporomandibular joint disorders
  81. Concentrations of dioxins, furans and dioxin-like PCBs in natural animal feed additives
  82. Structure and some physicochemical and functional properties of water treated under ammonia with low-temperature low-pressure glow plasma of low frequency
  83. Mesoscale nanoparticles encapsulated with emodin for targeting antifibrosis in animal models
  84. Amine-functionalized magnetic activated carbon as an adsorbent for preconcentration and determination of acidic drugs in environmental water samples using HPLC-DAD
  85. Antioxidant activity as a response to cadmium pollution in three durum wheat genotypes differing in salt-tolerance
  86. A promising naphthoquinone [8-hydroxy-2-(2-thienylcarbonyl)naphtho[2,3-b]thiophene-4,9-dione] exerts anti-colorectal cancer activity through ferroptosis and inhibition of MAPK signaling pathway based on RNA sequencing
  87. Synthesis and efficacy of herbicidal ionic liquids with chlorsulfuron as the anion
  88. Effect of isovalent substitution on the crystal structure and properties of two-slab indates BaLa2−xSmxIn2O7
  89. Synthesis, spectral and thermo-kinetics explorations of Schiff-base derived metal complexes
  90. An improved reduction method for phase stability testing in the single-phase region
  91. Comparative analysis of chemical composition of some commercially important fishes with an emphasis on various Malaysian diets
  92. Development of a solventless stir bar sorptive extraction/thermal desorption large volume injection capillary gas chromatographic-mass spectrometric method for ultra-trace determination of pyrethroids pesticides in river and tap water samples
  93. A turbidity sensor development based on NL-PI observers: Experimental application to the control of a Sinaloa’s River Spirulina maxima cultivation
  94. Deep desulfurization of sintering flue gas in iron and steel works based on low-temperature oxidation
  95. Investigations of metallic elements and phenolics in Chinese medicinal plants
  96. Influence of site-classification approach on geochemical background values
  97. Effects of ageing on the surface characteristics and Cu(ii) adsorption behaviour of rice husk biochar in soil
  98. Adsorption and sugarcane-bagasse-derived activated carbon-based mitigation of 1-[2-(2-chloroethoxy)phenyl]sulfonyl-3-(4-methoxy-6-methyl-1,3,5-triazin-2-yl) urea-contaminated soils
  99. Antimicrobial and antifungal activities of bifunctional cooper(ii) complexes with non-steroidal anti-inflammatory drugs, flufenamic, mefenamic and tolfenamic acids and 1,10-phenanthroline
  100. Application of selenium and silicon to alleviate short-term drought stress in French marigold (Tagetes patula L.) as a model plant species
  101. Screening and analysis of xanthine oxidase inhibitors in jute leaves and their protective effects against hydrogen peroxide-induced oxidative stress in cells
  102. Synthesis and physicochemical studies of a series of mixed-ligand transition metal complexes and their molecular docking investigations against Coronavirus main protease
  103. A study of in vitro metabolism and cytotoxicity of mephedrone and methoxetamine in human and pig liver models using GC/MS and LC/MS analyses
  104. A new phenyl alkyl ester and a new combretin triterpene derivative from Combretum fragrans F. Hoffm (Combretaceae) and antiproliferative activity
  105. Erratum
  106. Erratum to: A one-step incubation ELISA kit for rapid determination of dibutyl phthalate in water, beverage and liquor
  107. Review Articles
  108. Sinoporphyrin sodium, a novel sensitizer for photodynamic and sonodynamic therapy
  109. Natural products isolated from Casimiroa
  110. Plant description, phytochemical constituents and bioactivities of Syzygium genus: A review
  111. Evaluation of elastomeric heat shielding materials as insulators for solid propellant rocket motors: A short review
  112. Special Issue on Applied Biochemistry and Biotechnology 2019
  113. An overview of Monascus fermentation processes for monacolin K production
  114. Study on online soft sensor method of total sugar content in chlorotetracycline fermentation tank
  115. Studies on the Anti-Gouty Arthritis and Anti-hyperuricemia Properties of Astilbin in Animal Models
  116. Effects of organic fertilizer on water use, photosynthetic characteristics, and fruit quality of pear jujube in northern Shaanxi
  117. Characteristics of the root exudate release system of typical plants in plateau lakeside wetland under phosphorus stress conditions
  118. Characterization of soil water by the means of hydrogen and oxygen isotope ratio at dry-wet season under different soil layers in the dry-hot valley of Jinsha River
  119. Composition and diurnal variation of floral scent emission in Rosa rugosa Thunb. and Tulipa gesneriana L.
  120. Preparation of a novel ginkgolide B niosomal composite drug
  121. The degradation, biodegradability and toxicity evaluation of sulfamethazine antibiotics by gamma radiation
  122. Special issue on Monitoring, Risk Assessment and Sustainable Management for the Exposure to Environmental Toxins
  123. Insight into the cadmium and zinc binding potential of humic acids derived from composts by EEM spectra combined with PARAFAC analysis
  124. Source apportionment of soil contamination based on multivariate receptor and robust geostatistics in a typical rural–urban area, Wuhan city, middle China
  125. Special Issue on 13th JCC 2018
  126. The Role of H2C2O4 and Na2CO3 as Precipitating Agents on The Physichochemical Properties and Photocatalytic Activity of Bismuth Oxide
  127. Preparation of magnetite-silica–cetyltrimethylammonium for phenol removal based on adsolubilization
  128. Topical Issue on Agriculture
  129. Size-dependent growth kinetics of struvite crystals in wastewater with calcium ions
  130. The effect of silica-calcite sedimentary rock contained in the chicken broiler diet on the overall quality of chicken muscles
  131. Physicochemical properties of selected herbicidal products containing nicosulfuron as an active ingredient
  132. Lycopene in tomatoes and tomato products
  133. Fluorescence in the assessment of the share of a key component in the mixing of feed
  134. Sulfur application alleviates chromium stress in maize and wheat
  135. Effectiveness of removal of sulphur compounds from the air after 3 years of biofiltration with a mixture of compost soil, peat, coconut fibre and oak bark
  136. Special Issue on the 4th Green Chemistry 2018
  137. Study and fire test of banana fibre reinforced composites with flame retardance properties
  138. Special Issue on the International conference CosCI 2018
  139. Disintegration, In vitro Dissolution, and Drug Release Kinetics Profiles of k-Carrageenan-based Nutraceutical Hard-shell Capsules Containing Salicylamide
  140. Synthesis of amorphous aluminosilicate from impure Indonesian kaolin
  141. Special Issue on the International Conf on Science, Applied Science, Teaching and Education 2019
  142. Functionalization of Congo red dye as a light harvester on solar cell
  143. The effect of nitrite food preservatives added to se’i meat on the expression of wild-type p53 protein
  144. Biocompatibility and osteoconductivity of scaffold porous composite collagen–hydroxyapatite based coral for bone regeneration
  145. Special Issue on the Joint Science Congress of Materials and Polymers (ISCMP 2019)
  146. Effect of natural boron mineral use on the essential oil ratio and components of Musk Sage (Salvia sclarea L.)
  147. A theoretical and experimental study of the adsorptive removal of hexavalent chromium ions using graphene oxide as an adsorbent
  148. A study on the bacterial adhesion of Streptococcus mutans in various dental ceramics: In vitro study
  149. Corrosion study of copper in aqueous sulfuric acid solution in the presence of (2E,5E)-2,5-dibenzylidenecyclopentanone and (2E,5E)-bis[(4-dimethylamino)benzylidene]cyclopentanone: Experimental and theoretical study
  150. Special Issue on Chemistry Today for Tomorrow 2019
  151. Diabetes mellitus type 2: Exploratory data analysis based on clinical reading
  152. Multivariate analysis for the classification of copper–lead and copper–zinc glasses
  153. Special Issue on Advances in Chemistry and Polymers
  154. The spatial and temporal distribution of cationic and anionic radicals in early embryo implantation
  155. Special Issue on 3rd IC3PE 2020
  156. Magnetic iron oxide/clay nanocomposites for adsorption and catalytic oxidation in water treatment applications
  157. Special Issue on IC3PE 2018/2019 Conference
  158. Exergy analysis of conventional and hydrothermal liquefaction–esterification processes of microalgae for biodiesel production
  159. Advancing biodiesel production from microalgae Spirulina sp. by a simultaneous extraction–transesterification process using palm oil as a co-solvent of methanol
  160. Topical Issue on Applications of Mathematics in Chemistry
  161. Omega and the related counting polynomials of some chemical structures
  162. M-polynomial and topological indices of zigzag edge coronoid fused by starphene
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